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Merged
merged 3 commits into from
Oct 20, 2025
Merged

Consistently error on full circle of circular import aliases #1904

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e038de5
Consistently error on full circle of circular import aliases
ahejlsberg Oct 18, 2025
312160d
Accept new baselines
ahejlsberg Oct 18, 2025
a586c95
Stop skipping circularity tests when checking concurrently
ahejlsberg Oct 19, 2025
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1 change: 0 additions & 1 deletion internal/ast/symbol.go
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Expand Up @@ -43,7 +43,6 @@ const (
InternalSymbolNameClass = InternalSymbolNamePrefix + "class" // Unnamed class expression
InternalSymbolNameFunction = InternalSymbolNamePrefix + "function" // Unnamed function expression
InternalSymbolNameComputed = InternalSymbolNamePrefix + "computed" // Computed property name declaration with dynamic name
InternalSymbolNameResolving = InternalSymbolNamePrefix + "resolving" // Indicator symbol used to mark partially resolved type aliases
InternalSymbolNameInstantiationExpression = InternalSymbolNamePrefix + "instantiationExpression" // Instantiation expressions
InternalSymbolNameImportAttributes = InternalSymbolNamePrefix + "importAttributes"
InternalSymbolNameExportEquals = "export=" // Export assignment symbol
Expand Down
23 changes: 10 additions & 13 deletions internal/checker/checker.go
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Expand Up @@ -61,6 +61,7 @@ const (
TypeSystemPropertyNameResolvedBaseTypes
TypeSystemPropertyNameWriteType
TypeSystemPropertyNameInitializerIsUndefined
TypeSystemPropertyNameAliasTarget
)

type TypeResolution struct {
Expand Down Expand Up @@ -618,7 +619,6 @@ type Checker struct {
argumentsSymbol *ast.Symbol
requireSymbol *ast.Symbol
unknownSymbol *ast.Symbol
resolvingSymbol *ast.Symbol
unresolvedSymbols map[string]*ast.Symbol
errorTypes map[string]*Type
globalThisSymbol *ast.Symbol
Expand Down Expand Up @@ -915,7 +915,6 @@ func NewChecker(program Program) *Checker {
c.argumentsSymbol = c.newSymbol(ast.SymbolFlagsProperty, "arguments")
c.requireSymbol = c.newSymbol(ast.SymbolFlagsProperty, "require")
c.unknownSymbol = c.newSymbol(ast.SymbolFlagsProperty, "unknown")
c.resolvingSymbol = c.newSymbol(ast.SymbolFlagsNone, ast.InternalSymbolNameResolving)
c.unresolvedSymbols = make(map[string]*ast.Symbol)
c.errorTypes = make(map[string]*Type)
c.globalThisSymbol = c.newSymbolEx(ast.SymbolFlagsModule, "globalThis", ast.CheckFlagsReadonly)
Expand Down Expand Up @@ -15634,29 +15633,25 @@ func (c *Checker) resolveAlias(symbol *ast.Symbol) *ast.Symbol {
}
links := c.aliasSymbolLinks.Get(symbol)
if links.aliasTarget == nil {
links.aliasTarget = c.resolvingSymbol
if !c.pushTypeResolution(symbol, TypeSystemPropertyNameAliasTarget) {
return c.unknownSymbol
}
node := c.getDeclarationOfAliasSymbol(symbol)
if node == nil {
panic("Unexpected nil in resolveAlias for symbol: " + c.symbolToString(symbol))
}
target := c.getTargetOfAliasDeclaration(node, false /*dontRecursivelyResolve*/)
if links.aliasTarget == c.resolvingSymbol {
if target == nil {
target = c.unknownSymbol
}
links.aliasTarget = target
} else {
links.aliasTarget = core.OrElse(c.getTargetOfAliasDeclaration(node, false /*dontRecursivelyResolve*/), c.unknownSymbol)
if !c.popTypeResolution() {
c.error(node, diagnostics.Circular_definition_of_import_alias_0, c.symbolToString(symbol))
links.aliasTarget = c.unknownSymbol
}
} else if links.aliasTarget == c.resolvingSymbol {
links.aliasTarget = c.unknownSymbol
}
return links.aliasTarget
}

func (c *Checker) tryResolveAlias(symbol *ast.Symbol) *ast.Symbol {
links := c.aliasSymbolLinks.Get(symbol)
if links.aliasTarget != c.resolvingSymbol {
if links.aliasTarget != nil || c.findResolutionCycleStartIndex(symbol, TypeSystemPropertyNameAliasTarget) < 0 {
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Hopefully this extra find isn't too expensive, given how often we resolve aliases.

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tryResolveAlias is only called when generating spelling correction suggestions, so not an issue at all. And anyway, every call to pushTypeResolution has a call to that find method with no issues.

return c.resolveAlias(symbol)
}
return nil
Expand Down Expand Up @@ -18079,6 +18074,8 @@ func (c *Checker) typeResolutionHasProperty(r *TypeResolution) bool {
return c.nodeLinks.Get(r.target.(*ast.Node)).flags&NodeCheckFlagsInitializerIsUndefinedComputed != 0
case TypeSystemPropertyNameWriteType:
return c.valueSymbolLinks.Get(r.target.(*ast.Symbol)).writeType != nil
case TypeSystemPropertyNameAliasTarget:
return c.aliasSymbolLinks.Get(r.target.(*ast.Symbol)).aliasTarget != nil
}
panic("Unhandled case in typeResolutionHasProperty")
}
Expand Down
5 changes: 0 additions & 5 deletions internal/testrunner/compiler_runner.go
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Expand Up @@ -337,11 +337,6 @@ func newCompilerTest(
}

var concurrentSkippedErrorBaselines = map[string]string{
"circular1.ts": "Circular error reported in an extra position.",
"circular3.ts": "Circular error reported in an extra position.",
"recursiveExportAssignmentAndFindAliasedType1.ts": "Circular error reported in an extra position.",
"recursiveExportAssignmentAndFindAliasedType2.ts": "Circular error reported in an extra position.",
"recursiveExportAssignmentAndFindAliasedType3.ts": "Circular error reported in an extra position.",
"typeOnlyMerge2.ts": "Type-only merging is not detected when files are checked on different checkers.",
"typeOnlyMerge3.ts": "Type-only merging is not detected when files are checked on different checkers.",
}
Expand Down
5 changes: 4 additions & 1 deletion testdata/baselines/reference/submodule/compiler/circularModuleImports.errors.txt
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Original file line number Diff line number Diff line change
@@ -1,7 +1,8 @@
circularModuleImports.ts(5,5): error TS2303: Circular definition of import alias 'A'.
circularModuleImports.ts(7,5): error TS2303: Circular definition of import alias 'B'.


==== circularModuleImports.ts (1 errors) ====
==== circularModuleImports.ts (2 errors) ====
module M

{
Expand All @@ -11,6 +12,8 @@ circularModuleImports.ts(5,5): error TS2303: Circular definition of import alias
!!! error TS2303: Circular definition of import alias 'A'.

import B = A;
~~~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'B'.

}

23 changes: 23 additions & 0 deletions testdata/baselines/reference/submodule/compiler/circularModuleImports.errors.txt.diff
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@@ -0,0 +1,23 @@
--- old.circularModuleImports.errors.txt
+++ new.circularModuleImports.errors.txt
@@= skipped -0, +0 lines =@@
circularModuleImports.ts(5,5): error TS2303: Circular definition of import alias 'A'.
-
-
-==== circularModuleImports.ts (1 errors) ====
+circularModuleImports.ts(7,5): error TS2303: Circular definition of import alias 'B'.
+
+
+==== circularModuleImports.ts (2 errors) ====
module M

{
@@= skipped -10, +11 lines =@@
!!! error TS2303: Circular definition of import alias 'A'.

import B = A;
+ ~~~~~~~~~~~~~
+!!! error TS2303: Circular definition of import alias 'B'.

}

7 changes: 5 additions & 2 deletions testdata/baselines/reference/submodule/compiler/declarationEmitUnknownImport.errors.txt
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Original file line number Diff line number Diff line change
@@ -1,14 +1,17 @@
declarationEmitUnknownImport.ts(1,1): error TS2303: Circular definition of import alias 'Foo'.
declarationEmitUnknownImport.ts(1,14): error TS2304: Cannot find name 'SomeNonExistingName'.
declarationEmitUnknownImport.ts(1,14): error TS2503: Cannot find namespace 'SomeNonExistingName'.
declarationEmitUnknownImport.ts(2,9): error TS2303: Circular definition of import alias 'Foo'.


==== declarationEmitUnknownImport.ts (3 errors) ====
==== declarationEmitUnknownImport.ts (4 errors) ====
import Foo = SomeNonExistingName
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'Foo'.
~~~~~~~~~~~~~~~~~~~
!!! error TS2304: Cannot find name 'SomeNonExistingName'.
~~~~~~~~~~~~~~~~~~~
!!! error TS2503: Cannot find namespace 'SomeNonExistingName'.
export {Foo}
export {Foo}
~~~
!!! error TS2303: Circular definition of import alias 'Foo'.
22 changes: 22 additions & 0 deletions testdata/baselines/reference/submodule/compiler/declarationEmitUnknownImport.errors.txt.diff
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@@ -0,0 +1,22 @@
--- old.declarationEmitUnknownImport.errors.txt
+++ new.declarationEmitUnknownImport.errors.txt
@@= skipped -0, +0 lines =@@
declarationEmitUnknownImport.ts(1,1): error TS2303: Circular definition of import alias 'Foo'.
declarationEmitUnknownImport.ts(1,14): error TS2304: Cannot find name 'SomeNonExistingName'.
declarationEmitUnknownImport.ts(1,14): error TS2503: Cannot find namespace 'SomeNonExistingName'.
-
-
-==== declarationEmitUnknownImport.ts (3 errors) ====
+declarationEmitUnknownImport.ts(2,9): error TS2303: Circular definition of import alias 'Foo'.
+
+
+==== declarationEmitUnknownImport.ts (4 errors) ====
import Foo = SomeNonExistingName
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'Foo'.
@@= skipped -11, +12 lines =@@
~~~~~~~~~~~~~~~~~~~
!!! error TS2503: Cannot find namespace 'SomeNonExistingName'.
export {Foo}
+ ~~~
+!!! error TS2303: Circular definition of import alias 'Foo'.
7 changes: 5 additions & 2 deletions testdata/baselines/reference/submodule/compiler/declarationEmitUnknownImport2.errors.txt
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Expand Up @@ -3,9 +3,10 @@ declarationEmitUnknownImport2.ts(1,12): error TS1005: '=' expected.
declarationEmitUnknownImport2.ts(1,12): error TS2304: Cannot find name 'From'.
declarationEmitUnknownImport2.ts(1,12): error TS2503: Cannot find namespace 'From'.
declarationEmitUnknownImport2.ts(1,17): error TS1005: ';' expected.
declarationEmitUnknownImport2.ts(2,1): error TS2303: Circular definition of import alias 'Foo'.


==== declarationEmitUnknownImport2.ts (5 errors) ====
==== declarationEmitUnknownImport2.ts (6 errors) ====
import Foo From './Foo'; // Syntax error
~~~~~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'Foo'.
Expand All @@ -17,4 +18,6 @@ declarationEmitUnknownImport2.ts(1,17): error TS1005: ';' expected.
!!! error TS2503: Cannot find namespace 'From'.
~~~~~~~
!!! error TS1005: ';' expected.
export default Foo
export default Foo
~~~~~~~~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'Foo'.
22 changes: 22 additions & 0 deletions ...data/baselines/reference/submodule/compiler/declarationEmitUnknownImport2.errors.txt.diff
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@@ -0,0 +1,22 @@
--- old.declarationEmitUnknownImport2.errors.txt
+++ new.declarationEmitUnknownImport2.errors.txt
@@= skipped -2, +2 lines =@@
declarationEmitUnknownImport2.ts(1,12): error TS2304: Cannot find name 'From'.
declarationEmitUnknownImport2.ts(1,12): error TS2503: Cannot find namespace 'From'.
declarationEmitUnknownImport2.ts(1,17): error TS1005: ';' expected.
-
-
-==== declarationEmitUnknownImport2.ts (5 errors) ====
+declarationEmitUnknownImport2.ts(2,1): error TS2303: Circular definition of import alias 'Foo'.
+
+
+==== declarationEmitUnknownImport2.ts (6 errors) ====
import Foo From './Foo'; // Syntax error
~~~~~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'Foo'.
@@= skipped -15, +16 lines =@@
~~~~~~~
!!! error TS1005: ';' expected.
export default Foo
+ ~~~~~~~~~~~~~~~~~~
+!!! error TS2303: Circular definition of import alias 'Foo'.
5 changes: 4 additions & 1 deletion testdata/baselines/reference/submodule/compiler/exportAsNamespaceConflict.errors.txt
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@@ -1,9 +1,12 @@
/a.d.ts(2,1): error TS2303: Circular definition of import alias 'N'.
/a.d.ts(3,1): error TS2303: Circular definition of import alias 'N'.


==== /a.d.ts (1 errors) ====
==== /a.d.ts (2 errors) ====
declare global { namespace N {} }
export = N;
~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'N'.
export as namespace N;
~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'N'.
Expand Down
16 changes: 16 additions & 0 deletions testdata/baselines/reference/submodule/compiler/exportAsNamespaceConflict.errors.txt.diff
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@@ -0,0 +1,16 @@
--- old.exportAsNamespaceConflict.errors.txt
+++ new.exportAsNamespaceConflict.errors.txt
@@= skipped -0, +0 lines =@@
+/a.d.ts(2,1): error TS2303: Circular definition of import alias 'N'.
/a.d.ts(3,1): error TS2303: Circular definition of import alias 'N'.


-==== /a.d.ts (1 errors) ====
+==== /a.d.ts (2 errors) ====
declare global { namespace N {} }
export = N;
+ ~~~~~~~~~~~
+!!! error TS2303: Circular definition of import alias 'N'.
export as namespace N;
~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2303: Circular definition of import alias 'N'.
5 changes: 4 additions & 1 deletion testdata/baselines/reference/submodule/conformance/circular1.errors.txt
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@@ -1,8 +1,11 @@
/a.ts(1,15): error TS2303: Circular definition of import alias 'A'.
/b.ts(1,15): error TS2303: Circular definition of import alias 'A'.


==== /a.ts (0 errors) ====
==== /a.ts (1 errors) ====
export type { A } from './b';
~
!!! error TS2303: Circular definition of import alias 'A'.

==== /b.ts (1 errors) ====
export type { A } from './a';
Expand Down
15 changes: 15 additions & 0 deletions testdata/baselines/reference/submodule/conformance/circular1.errors.txt.diff
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@@ -0,0 +1,15 @@
--- old.circular1.errors.txt
+++ new.circular1.errors.txt
@@= skipped -0, +0 lines =@@
+/a.ts(1,15): error TS2303: Circular definition of import alias 'A'.
/b.ts(1,15): error TS2303: Circular definition of import alias 'A'.


-==== /a.ts (0 errors) ====
+==== /a.ts (1 errors) ====
export type { A } from './b';
+ ~
+!!! error TS2303: Circular definition of import alias 'A'.

==== /b.ts (1 errors) ====
export type { A } from './a';
13 changes: 11 additions & 2 deletions testdata/baselines/reference/submodule/conformance/circular3.errors.txt
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@@ -1,13 +1,22 @@
/a.ts(1,15): error TS2303: Circular definition of import alias 'A'.
/a.ts(2,15): error TS2303: Circular definition of import alias 'B'.
/b.ts(1,15): error TS2303: Circular definition of import alias 'B'.
/b.ts(2,15): error TS2303: Circular definition of import alias 'A'.


==== /a.ts (0 errors) ====
==== /a.ts (2 errors) ====
import type { A } from './b';
~
!!! error TS2303: Circular definition of import alias 'A'.
export type { A as B };
~~~~~~
!!! error TS2303: Circular definition of import alias 'B'.

==== /b.ts (1 errors) ====
==== /b.ts (2 errors) ====
import type { B } from './a';
~
!!! error TS2303: Circular definition of import alias 'B'.
export type { B as A };
~~~~~~
!!! error TS2303: Circular definition of import alias 'A'.

29 changes: 29 additions & 0 deletions testdata/baselines/reference/submodule/conformance/circular3.errors.txt.diff
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@@ -0,0 +1,29 @@
--- old.circular3.errors.txt
+++ new.circular3.errors.txt
@@= skipped -0, +0 lines =@@
+/a.ts(1,15): error TS2303: Circular definition of import alias 'A'.
+/a.ts(2,15): error TS2303: Circular definition of import alias 'B'.
/b.ts(1,15): error TS2303: Circular definition of import alias 'B'.
-
-
-==== /a.ts (0 errors) ====
+/b.ts(2,15): error TS2303: Circular definition of import alias 'A'.
+
+
+==== /a.ts (2 errors) ====
import type { A } from './b';
+ ~
+!!! error TS2303: Circular definition of import alias 'A'.
export type { A as B };
+ ~~~~~~
+!!! error TS2303: Circular definition of import alias 'B'.

-==== /b.ts (1 errors) ====
+==== /b.ts (2 errors) ====
import type { B } from './a';
~
!!! error TS2303: Circular definition of import alias 'B'.
export type { B as A };
+ ~~~~~~
+!!! error TS2303: Circular definition of import alias 'A'.